Catalytic gas generation using a hydrazine with an oxidizer on an inert substrate

ABSTRACT

A gas generation scheme in which an inert porous support material, substrate or carrier, is heated sufficiently to maintain decomposition of a liquid monopropellant by a hypergolic or spontaneous exothermic reaction between the liquid monopropellant and a suitable oxidizing agent.

te States Muriree, Jr. et a1.

5 atet [451 Sept. 11, 1973 CATALYTIC GAS GENERATION USING A HYDRAZINEWITH AN OXTDIZER ON AN INERT SUBSTRATE [75] Inventors: James A. Murfree,Jr., Huntsville;

Billy J. Sandlin, Athens; William A. Duncan, Huntsville, all of Ala.

[73] Assignee: The United States of America as represented by theSecretary of the Army, Washington, DC.

[22] Filed: July 5, 1967 [21] Appl. No.: 651,654

[52] [1.5. CI. 60/219, 149/36 [51] Int. Cl C06d 5/10 {58] Field ofSearch 149/36; 60/219, 220,

[56] References Cited V UNITED STATES PATENTS 2,925,709 2/1960 Mantellet al 149/36 X 2,930,184 3/1960 Plescia et al 149/36 X 3,021,667 2/1962Griffin et a1. 149/36 X 3,083,527 4/1963 Fox 60/220 X 3,086,945 4/1963Cohn 149/36 X 3,331,203 7/1967 Kaufman et a1. 60/220 PrimaryExaminerBenjamin R. Padgett AttorneyHarry M. Saragovitz, Edward J.Kelly, Herbert Berl and Elihu L. Turetsky [57] ABSTRACT A gas generationscheme in which an inert porous support material, substrate or carrier,is heated sufficiently to maintain decomposition of a liquidmonopropellant by a hypergolic or spontaneous exothermic reactionbetween the liquid monopropellant and a suitable oxidizing agent.

7 Claims, 4 Drawing Figures mmmsm 1 e915 757, 529

James A. Murfree Jr. Billy J. Scmdlin William A. Duncan INVENTORS.

CATALYTIC GAS GENERATION USING A I-IYDRAZINE WITH AN OXIDIZER ON ANINERT SUBSTRATE BACKGROUND OF THE INVENTION This invention relates to agas generation scheme, and in particular to one employing a liquidmonopropellant, an initiator and an .inert porous support material whichsupports the initiator.

The development of reliable, useful monopropellant liquid gas generatorsfor use in missiles is a pressing problem and the subject of muchresearch. Much work has been done on the catalytic decomposition ofhydrazine and similar fuels for gas generation. These schemes utilize aninert carrier supporting a nonreactive and non-consumed coating of anactive catalytic agent which rapidly and spontaneously decomposeshydrazine into the gases nitrogen, hydrogen and ammonia. These catalyticdecomposition schemes, thus, allow numerous restarts and make an on-offoperation feasible since the catalyst is not consumed. However, the moreactive and better catalysts are expensive (greater than $l,000/lb.),Therefore, less expensive catalysts or the development of newdecomposition schemes for monopropellants which meet the requirementsfor gas generation applications in missiles are very desirable.

SUMMARY OF THE INVENTION It has been discovered that a gas generator canbe provided by supporting certain oxidizing agents in certain inertporous solid support materials and bringing an exothermally decomposingmonopropellant such as hydrazine into contact with the oxidizing agent.The monopropellant and oxidizing agent, when brought together, react toproduce gas and heat. The thus heated support material causesdecomposition of the liquid monopropellant. The inert porous supportmaterial not only serves to support the initiator but also serves as adecomposition bed maintaining a sufficient temperature to sustain thedecomposition of the liquid monopropellant once the initiator has beenconsumed. By maintaining a sufficient temperature during the off phaseso that when the propellant is readmitted, spontaneous decompositionrecommences, an on-off operational capability is made possible.

BRIEF DESCRIPTION OF THE DRAWING This invention and objects andadvantages thereof will become more clearly understood by reference tothe following detailed description, of which the accompanying drawingforms an integral part thereof, and in which:

FIG. 1 is a perspective view, shown partially cut away, of a gasgenerating bed of this invention inside a gas generator housing;

FIG. 2 is a cross-sectional view of the gas generating bed of FIG. 1;

FIG. 3 is a cross-sectional view of an alternative embodiment of a gasgenerating bed of this invention; and,

FIG. 4 is a cross-sectional view of another alternative embodiment of agas generating bed of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An inert porous supportmaterial is employed to support certain oxidizing agents for use asinitiators in gas generators incorporating exothermally decomposingliquid monopropellants. Monopropellants which have been satisfactorilyused in this scheme of gas generation are hydrazine and hydrazine-typefuels (e.g., 1,1-dimethylhydrazine and monomethylhydrazine Mixturesthereof may be particularly desirable in certain instances. Note,however, that almost any exothermally decomposing monopropellant may beused.

Initiators (oxidizing agents) which have been satisfactorily used arepotassium permanganate, potassium dichromate, iodic acid, iodicanhydride and calcium permanganate. Other oxidizing agents and mixturesthereof may also be used as initiators, provided the oxidizing agentused reacts vigorously with the monopropellant. Note, however, that notevery oxidizing agent will work with every exothermally decomposingmonopropellant. In particular, potassium permanganate will not work with1,1-dimethylhydrazine. With this exception, any of the five specificoxidizing agents given above will generally work with any exothermallydecomposing monopropellant. Accordingly, the term suitable oxidizingagent is defined herein to mean an oxidizing agent that will react withthe particular monopropellant chosen. Inert porous support materials forthe initiator which have been satisfactorily employed are activatedcharcoal, silica gel, alumina, porous firebrick and similar refractorymaterials. The support material, thus, acts as a substrate or carrierfor the initiator, and a porosity of from about 65% to about has beensatisfactorily employed.

There are numerous methods of utilizing the support or carrier in a bedfor the decomposition. The support can be in the form of granules orpellets contained in a suitable housing, or it may be a single piece ofthe support material with sufficient porosity to allow passage'of theliquid monopropellant and decomposition gases.

EXAMPLE 1 A specific example of this invention is one which useshydrazine as the liquid monopropellant, potassium permanganate as theinitiator, and porous firebrick as the support and decomposition bed.FIGS. 1 and 2 show an arrangement for this example. A sandwich design isused; i.e., a layer of initiator 10 is placed between two layers offirebrick l2 and 14. The firebrick and initiator are enclosed in sleeve16, and a pressurized injector (not shown) andinjector plate 18 are usedto inject the monopropellant through holes 20 into the firebrick andinitiator. The firebrick layers 12 and 14 are secured to sleeve 16 by arefractory adhesive. Sleeve 16, which surrounds the firebrick, isenclosed in a gas generator housing 22 in a conventional manner. A wireretaining screen 11 (or other perforated support) is secured to the gasgenerator housing 22 in a conventional manner.

EXAMPLE 2 Another example of this invention is one which usesmonomethylhydrazine as a liquid monopropellant, calcium permanganate asthe initiator, and porous firebrick as the support and decompositionbed. FIG. 3

EXAMPLE 3 Still another example of this invention is one which uses 1,l-dimethylhydrazine as the liquid monopropellant, iodic acid dispersedin porous firebrick as the initiator, and porous firebrick as thesupport and decomposition bed. As illustrated in FIG. 4, the gasgenerating bed of which is substituted for the gas generating bed ofFIG. 2 or FIG. 3 and adapted to be placed in the gas generator housing22 of FIG. 1, porous firebrick support 30 is secured to sleeve 32 by aregractory adhesive. Injector plate 18 is utilized to inject themonopropellant through holes 20 into the firebrick with the initiatorsupported therein. A wire retaining screen 11 (or other perforatedsupport) is secured to the gas generator housing 22 in a conventionalmanner.

The mode of operation of this invention is as follows: The initiator isput in or on the support or bed such that when the monopropellant isadmitted to the bed, it reacts rapidly and vigorously with the initiatorwhich is consumed in the reaction. The initial reaction also decomposesthe monopropellant with resultant gas for mation. The reaction betweenthe monopropellant and initiator generates sufficient heat to bring thesupport up to a sufficient temperature to maintain the decomposition,with gas generation, of the monopropellant throughout the requiredoperational time of the gas generator, even after the initiator has beenconsumed.

On-off operational capability is also possible since the support ismaintained at a sufficient temperature for a few minutes during the offphase so that when the propellant is readmitted, spontaneousdecomposition recommences.

Various other modifications and variations of this invention will bereaily apparent to those skilled in the art in the light of the aboveteachings which are within the spirit and scope of this invention. I

We claim:

1. The process of gas generation comprising: providing an inert poroussupport material; supporting an inorganic oxidizing agent selected frompotassium permanganate, potassium dichromate, iodic acid, iodicanhydride and calcium permanganate in said inert support material; andbringing an exothermally decomposing liquid monopropellant selected fromhydrazine, l,l-dimethylhydrazine, mixtures thereof into contact withsaid inert support material and said oxidizing agent to cause saidliquid monopropellant and said oxidizing agent to react with theliberation of heat and gas and thereby heat said inert support materialto a temperature sufficient to maintain decomposition of said liquidmonopropellant after said oxidizing agent is expended.

2. The process of claim 1 wherein said liquid monopropellant ishydrazine, vl,l-dimethylhydrazine or monomethylyhdrazine.

3. The process of claim 1 wherein said inert porous support material isactivated charcoal, silica gel, alumina or porous firebrick.

4. The process of claim 1 wherein said liquid monopropellant ishydrazine, l,l-dimethylhydrazine or monomethylhydrazine and said inertporous support material is activated charcoal, silica gel, alumina orporous firebrick.

5. The process of claim 1 wherein said liquid monopropellant ishydrazine or monomethylhydrazine.

6. The process of claim 1 wherein said liquid monopropellant ishydrazine or monomethylhydrazine and said inert porous support materialis activated charcoal, silica gel, alumina or porous firebrick.

7. The process of claim 1 wherein said liquid monopropellant ishydrazine, l,l-dimethylhydrazine or monomethylhydrazine and saidoxidizing agent is potassium dichromate, iodic acid, iodic anhydride orcalcium permanganate.

monomethylhydrazine and-

2. The process of claim 1 wherein said liquid monopropellant ishydrazine, 1,1-dimethylhydrazine or monomethylyhdrazine.
 3. The processof claim 1 wherein said inert porous support material is activatedcharcoal, silica gel, alumina or porous firebrick.
 4. The process ofclaim 1 wherein said liquid monopropellant is hydrazine,1,1-dimethylhydrazine or monomethylhydrazine and said inert poroussupport material is activated charcoal, silica gel, alumina or porousfirebrick.
 5. The process of claim 1 wherein said liquid monopropellantis hydrazine or monomethylhydrazine.
 6. The process of claim 1 whereinsaid liquid monopropellant is hydrazine or monomethylhydrazine and saidinert porous support material is activated charcoal, silica gel, aluminaor porous firebrick.
 7. The process of claim 1 wherein said liquidmonopropellant is hydrazine, 1,1-dimethylhydrazine ormonomethylhydrazine and said oxidizing agent is potassium dichromate,iodic acid, iodic anhydride or calcium permanganate.